Photographic layers which contain uv-absorbers

ABSTRACT

THE LIGHT STABILITY OF COLOR PHOTOGRAPHIC IMAGES IS IMPROVED BY COVERCOATING THE IMAGE CARRYING LAYER WITH A UVPROTECTIVE COATING WHICH CONTAINS A UV-ABSORBING COMPOUND. THE UV-ABSORBING LAYER CONTAINS AS UV-ABSORBENT A 2-PHENOLBENZOTRIAZOLE, THE BENZO RING OF WHICH IS SUBSTITUTED WITH 2 BUTYL GROUPS.

United States Patent Office 3,794,493 PHOTOGRAPHIC LAYERS WHICH CONTAINUV-ABSORBERS Johannes Sobel, Leverkusen, Fritz Nittel and WillibaldPelz, Cologne, and Wolfgang Himmelmann, Opladen, Germany, assignors toAgfa-Gevaert Aktiengesellschaft, Leverkusen, Germany No Drawing. FiledJune 17, 1971, Ser. No. 154,229 Claims priority, application Germany,July 24, 1970, P 20 36 719.5; Switzerland, June 19, 1970, 9,319/70 Int.Cl. G03c 1/ 84 U.S. Cl. 95 -84 R 6 Claims ABSTRACT OF THE DISCLOSURE Thelight stability of color photographic images is improved by overcoatingthe image carrying layer with a UV- protective coating which contains aUV-absorbing compound.

The UV-absorbing layer contains as UV-absorbent a 2-phenolbenzotriazole,the benzo ring of which is substituted with 2 butyl groups.

The invention relates to photographic layers which contain UV-absorbentcompounds.

Numerous compounds are known which absorb light in the UV-region of thespectrum and are, therefore, suitable for the production of UV-filtersand UV-protective coatings. Such coatings are used in photographicmaterial for increasing the light fastness of color images. The UV-absorbent compounds should be incorporated in a separate protectivelayer in as high a concentration as possible in order to achieve thegreatest possible effect. Generally, it is not possible to use theUV-absorbent compounds homogeneously or heterogeneously distributed withthe image dyes in one layer, because the absorbent compounds and thedyes are very frequently found to interact with each other so thatbleaching of the image is increased. The UV-absorbent compounds shouldbe colorless and should have a high coefficient of extinction in theUV-region and should be as stable as possible.

The UV-absorbent compounds can be used in many different ways, e.g. inWater insoluble binders. In this case, the finished color image iscoated with such a solution in a separate working step. This procedure,however, is only economical for images of large shapes and sizes and is,therefore, not generally applicable. Incorporation of water soluble andwater insoluble UV-ab sorbent compounds in a diffusion fast manner in aprotective layer has also been described. In this case, the chemical andphysical properties of the UV-absorbent compound must meet certainrequirements, e.g. it must be possible for the absorbent compound to beused in a highly concentrated form in layers of a thickness of 1 to 2,um. without precipitating from the protective layer in the form ofcrystals or an oil. The UV absorbent compound must, of course, be inerttowards photographic processing baths and must not undergo yellowing onexposure to light.

A very wide variety of UV-absorbent compounds have already beendescribed for the present purpose. Many of these compounds, however, donot sufficiently satisfy the requirements in practice. Aromatic azineshave, inter alia, been particularly recommended as UV-absorbentcompounds, but these generally have a high melting point so that theyare diflicult to use because of their tendency to crystallize.Derivatives of this type which can easily be incorporated inphotographic layers, which are described in German Pat. No. 1,182,066,are slightly yellowish so that they are detrimental to the white colorimages. The reason for thls 1s that a slight absorption of light fromthe visible region of the spectrum occurs.

3,794,493 Patented Feb. 26, 1974 It is among the objects of the presentinvention to produce photographic layers which contain UV-absorbers,which must be easily incorporated in these layers, and as far aspossible, must absorb only in the UV-region of the spectrum.

We now have found a photographic material with a UV-absorbent layerwhich contains a UV-absorber of the following formula OH R R in which Rand R stand for sec.-butyl or tert.-butyl and R represents hydrogen,alkyl or alkoxy having up to 3 carbon atoms or halogen such as chlorineor bromine. But at least one of the substituents R and R representssec.- butyl. The phenol ring may also be further substituted e.g. byalkyl or alkoxy having up to 3 carbon atoms or halogen for examplechlorine or bromine. Particular utility is exhibited by the followingcompounds:

M.P.,C.

(1) N on clauses. 8H1

( J4H9(t31't.)

(2) N OH C H(sec.)

iHflsec.)

(3) N 0H C4Ho(tert.)

(S Hn(sec.)

4 N 0H C4Hg(sec.) 74 75 k/ /N \N/ lHQUJBl't.)

5 N OH C4H9(sec.) 79-80 C2Hs0- l \/\N (lhHflter-t.)

(6) N 0H C4H9(SGC.) 43-44 k \N H9(tert.)

7 N OH 04119 (sec.) 67-68 I \N JhHn (tert.)

s N 0H 0411mm. 72

\N JhHMsec.)

TABLEContinued M.P.,C.

(9) N OH C4Ha (sec.) 41-42 N JhHn (see) 10).-.- N OH 0.11. (sec.) on.

CnQ

(11) N OH C4Ha (500.) Oil.

The compounds to be used according to the invention are prepared inknown manner. Preferably one starts from a diazotized o-nitranilinewhich is coupled with the butyl-substituted phenol to yield theo-nitrophenylazo compounds. The last mentioned compounds are reduced inalkaline medium with zinc dust whereby the benzotriazols are formed.

The preparation of Compound 1 is described in the following:

COMPOUND 1 138 g. (1 mol) of o-nitraniline are stirred up with 500 ml.of concentrated aqueous hydrochloric acid, mixed with 750 m1. of waterand diazotized with 70 g. (1 mol) sodium nitrite in 150 ml. of water ata temperature of between and C. Thereafter it is stirred for anotherhalf hour.

The resulting diazonium solution is added quickly drop by drop whilestirring at a temperautre of 5 C. to a solution of 206 g.2-sec.-butyl-4-tert.-butyl-phenol (1 mol), 140 g. of sodium acetate and400 g. of concentrated (45%) aqueous sodium hydroxide in 2.3 l. ofmethanol. The mixture is stirred for some hours and left standing overnight.

The precipitated red dye is filtered off, washed with water and dried(M.P. ca. 80 C.). The raw product is recrystallized from methanol, theprecipitate filtered off and washed with cold methanol (M.P. 92-93 C.).

355 g. (1 mol) of 2-nitro-phenylazo-2-hydroxy-3'-sec.- butyl-S'-tert.butylbenzene are refluxed in 2.5 l. of ethanol and mixed with 520 g. ofsodium hydroxide in 2.5 1. water. Thereafter 230 g. of zinc dust areadded portionwise under intensive stirring and the reaction mixture isrefluxed until clarification the mixture. The non-reacted zinc dust isfiltered off and the pH of the yellow solution is adjusted by additionof aqueous hydrochloric acid to a value of between 3-4. The yellowprecipitate is recrystallized from methanol in the presence of charcoal.For further purification the yellow crystals can be recrystallized againfrom methanol or from light gasoline in the presence of bleaching earth.Yield: ca. 165 g.M.P. 80-81 C.

The other compounds can be prepared in a similar manner.

The UV-absorbent compounds which are to be used according to theinvention have exceptionally advantageous absorption properties. Theabsorption curve drops steeply at the beginning of the visible region ofthe spectrum.

The UV-absorbent compounds are readily soluble in those particularsolvents which are used as so-called oil forming agents for theproduction of color photographic materials. The solution can easily beemulsified in the casting solutions for the layers.

The UV-absorbent compounds to be used according to the invention mayalso be used in combination with other UV-absorbent compounds.

The UV-absorbent compounds do not deleteriously affect the photographicproperties of adjacent layers and in particular the color couplingreaction of dissolved dye derivatives is not reduced. Many of the knownUV-absorbent compounds even of the benztriazole series are detrimentalin this respect. The molar extinction coefficient is exceptionally high,so that the quantity of 'UV- absorbent compound used can be keptcomparatively low.

The UV-absorbent compounds are preferably emulsified in the castingsolutions for the particular layer in the form of their solutions inhigh boiling solvents, by using a suitable dispersing apparatus.

The proportions in which the UV-absorbent compounds are mixed with thesolvents may vary between 1:1 and 1:01. Low boiling auxiliary solventssuch as ethyl acetate, methylene chloride, alcohols and mixtures ofthese solvents may be used. After dispersion, the low boiling solv cutsare removed in thin layer evaporators under vacuum. Suitable waterinsoluble, high boiling compounds are, for example, dibutyl phthalate,tricresyl phosphate and particularly higher fatty acids, and preferablybranched fatty acids having about 10 to 20 C-atoms.

The UV-absorbent compounds may be added directly to the silver halideemulsions which contain color couplers or to a gelatin-containingsolution of the protective layer.

The gelatin layers which contain the UV-absorbent compound may bearranged in any position in the various layers of the photographicmaterial, but are preferably positioned above the layers which containthe image dye.

The UV-absorbent compounds are particularly suitable as the topmostlayer for photographic multi-layered materials of the usual arrangement.

The concentration of the UV-absorbent compounds in the layers may varywithin wide limits. An addition of 0.1-1.0 parts by weight, per part ofthe binding agent in the layer, has proved to be sufficient.

The binding agent for the UV-absorbing layers of the present inventionis preferably gelatine which however can be replaced partially accordingto a preferred embodiment of the invention by homoor copolymers ofacrylic or methacrylic acid esters with aliphatic alcohols having up to5 carbon atoms. In particular suitable are also anionic or cationicpolyurethanes as described in US. patent specifications Nos. 3,374,095and 3,397,989. The polyurethanes are also applied in combination withgelatine. The binding agents which are used in addition to gelatine areadded preferably from an aqueous latex of the polymer. The concentrationof the polymer in the layer is preferably 550% based on the total weightof the binding agent.

When using multi-layered color photographic materials, the concentrationof the UV-absorbing compounds is so chosen that on exposure to light thestability of the image dyes is equally satisfactory in the three layers.

The layer thickness of the protective layers which contain UV-absorbentcompounds is preferably 2 to 5 m.

After the usual color photographic processing and testing of theresulting color image for its light fastness, the color photographicmaterial is found to be improved by a factor of 4 to 10 compared withthe same color photo- 1graphic material which does not contain theseprotective ayers.

The improvement in fastness is determined by exposing both images at thesame color density to the same degree of bleaching. The ratio of luxhours required gives a measure of the improvement factor. Theimprovement factor depends not only on the concentration of theUV-absorbent izompound but also on the thickness of the protective ayer.

The layers which contain the UV-absorbent compound are completelytransparent in the dry state and practically colorless. They are stableagainst the photographic processing baths, e.g. a colorformingdevelopment bath. No yellowing can be detected after prolonged exposureto lg t.

Example 1 On to a paper support which is laminated on both sides with apolyethylene layer containing a white pigment are applied the followinglayers:

(1) a red-sensitive silver chloro bromide gelatine layer containing awater-soluble diifusion-resistant cyan coupler,

(2) an intermediate gelatine layer,

(3) a green-sensitive silver chloro bromide gelatine emulsion layercontaining a water-soluble diffusion-fast magenta coupler,

(4) an intermediate gelatine layer and (5) a silver bromide gelatineemulsion layer containing a yellow color coupler fast to diffusion.

On to a stripe of the above material is applied a gelatine layer havinga thickness of 3 p.111. Another stripe of the above material is coatedwith a UV-absorbing layer from the following casting emulsion:

30 g. of Compound 1 4.5 g. of sulfosuccinicacid-bis-(Z-ethyl)-hexylester 50 g. of a 30% methanolic solution of themonopotassium salt of pentadecylensuccinic acid (as described in Britishpatent specification 1,222,753 or US. application Ser. No. 814,808) aredissolved in 60 ml. of diethylcarbonate and emulsified at a temperatureof 55 C. into 1 l. of a aqueous gelatine solution.

The UV-absorbing layer has a thickness of 3am.

Both samples are processed in identical manner including exposure andcolor-forming development.

The light-fastness of the final image is determined as described above.The improvement factor lies in the range of 4-10 depending on the kindof the color coupler.

The UV-absorbing layer does not deleteriously affect the photographicproperties of the adjacent emulsion layers or the time of color-formingdevelopment. Formation of a uniform dye fog is not observed.

Example 2 The same procedure is applied as described in Example 1 butthe casting solution for the UV-absorbing layer is not applied as aseparate top layer but is added to the blue-sensitive silver halideemulsion layer containingthe yellow color coupler. The casting solutioncontaining the UV-absorbent is changed in so far as 50 g. of the sameUV-absorber and 75 g. of the 30% methanolic solution ofpentadecylensuccinic acid is used.

Similar results are obtained as in Example 1.

Example 3 The procedure is the same as described in Example 1 thecasting solution for the UV-absorbing layer has the followingcomposition:

Into 1 l. of a 10% aqueous solution of gelatine is emulsified at atemperature of 55 C. the following solution:

30 g. of Compound 1 4.5 g. of sulfosuccinicacid-bis-(2-ethyl)-hexylester 30 g. of a 30% methanolic solution of themonopotassium salt of pentadecylensuccinic acid 10 g. dibutylphthalatein 60 ml. of diethylcarbonate.

Similar results are obtained as in Example 1.

Example 4 The procedure is the same as described in Example 1. Thecasting solution for the UV-absorbing layer has the followingcomposition:

Into 1 l. of a 10% aqueous gelatine solution containing 50 g. of a 40%aqueous dispersion of an anionic polyurethane as described in US. patentspecification 3,374,095 is emulsified at a temperature of 55 C. thefollowing solution:

6 30 g. of Compound 2 3 g. of sulfosuccinicacid-bis-(2-ethyl)-hexylester and 50 g. of a 30% methanolic solution ofthe monopotassium salt of pentadecylensuccinic acid in 40 ml. ofdiethylcarbonate.

Similar results are obtained as in Example 1.

Example 5 30 g. of the UV-absorber referred to below 3 g. of thebis(2-ethyl)-hexylester of sulfossucinic acid in 60 g. of ethyl acetate.

Sample 1: UV-absor-ber Compound 1 Sample 2: UV-absorber Compound 2Sample 3: The UV-absorber of the following formula N\ HO N aHnGso) Theabove samples were stored at 40 C. and in the refrigerator and thebehaviour of the emulsions with respect to the precipitation of theUV-absorbing agents is observed. The results are shown in the followingtable.

Digestion Retrigerator Compound 1 hour 6 hours 24 hours 3 days 1 GoodGood.--" Good Good. 2.- do do do Do. A Slightly Orys- CompletelyCrystalerystallized. tallized. crystallized. lized.

It is readily apparent from the above results that the casting solutionsof the compounds used in accordance with the invention are far morestable, therefore far better to handle than the prior art compounds.

The above samples were also applied onto a processed multilayer colorphotographic material in the manner described in Example 1. Compounds ofthe invention do not crystallize in the layer. The protective action ofthe UV- absorbing layers containing compounds of the present inventionis considerably higher than the protective action of layers containingthe above prior art compound.

Precipitation of the UV-absorber of sample 3 can be reduced by asuificiently high addition of an oil former such as dibutylphthalate ortricresyl phosphate. The required amount of about 0.5 to 1 part byweight of oil former per part of UV-absorber is however so high that thelayers are getting hydrophobic which elfects processing of the exposedcolor-photographic material. The diffusion of the aqueous processingbaths into the photographic layers is made diflicult, which is inparticular relevant with hydrophilic color-forming developers such asN-butyl-N- w-sulfobutyl-p-phenylenediamine.

We claim:

1. A photographic element comprising a support, at least one hydrophilicphotographic silver halide emulsion layer and incorporated in one of thehydrophilic layers of said photographic element a UV-absorbing compoundof the following formula:

wherein represents R =sec.-butyl or tert.-butyl,

R =sec.-butyl or tert.-butyl, whereby at least one of the substituents Ror R stands for sec.-butyl and R =hydrogen, alkyl or alkoxy having up to3 carbon atoms or halogen.

2. The element of claim 1 wherein the UV-absorber is contained in anamount of 0.1-0.5 parts by weight per one part by weight of bindingagent of the layer.

3. The photographic element of claim 1 wherein the UV-absorbing compoundis finally distributed in the layer in the form of a solution in ahigh-boiling solvent.

4. The finished photographic element comprising a support having thereona plurality of developed and fixed photographic emulsion layerscontaining dye images formed upon color-forming development, at leastone of said dye images being subject to fading by the action ofultraviolet radiation, said emulsion layer containing the dye imagesubject to fading laying between said support and an UV-a'bsorbing layercontaining an ultraviolet absorbing compound of the following formula:

wherein represents R =sec.-butyl or tert.-butyl,

R =sec.-butyl or tert.-butyl, whereby at least one of the substituents Ror R stands for sec.-butyl and R =hydrogen, alkyl or alkoxy having up to3 carbon atoms or halogen.

UNITED STATES PATENTS 3,533,794 10/1970 Ohi et a1. 9684 R 3,649,2763/1972 Sano et a1 96-84 R RONALD H. SMITH, Primary Examiner US. Cl. X.R.

